KIEV (Reuters) - Thousands of supporters of Ukraine's re-energised opposition rallied outside parliament on Tuesday to press for early elections for the mayor of Kiev and oust an ally of President Viktor Yanukovich from the powerful post.

But despite the show of strength, Yanukovich's Party of the Regions defeated the attempt to set a June date for the ballot.

The outcome means that Yanukovich, whose first bid for power was doomed in 2004 by street protests in Kiev which became known as the "Orange Revolution", should be able to keep his man in control of the capital when he bids for a second term in 2015.

A crowd led by the three main opposition leaders marched from the centre of the capital to parliament, holding aloft banners calling for the release of jailed opposition leader Yulia Tymoshenko and denouncing Yanukovich's policies.

The protesters' direct target was Olexander Popov, appointed by Yanukovich as head of Kiev city's administration and now effectively mayor of the capital.

The Party of the Regions is pushing for the Kiev mayoral election to be delayed for two years until after the 2015 presidential election.

The last mayor, who left office in mid-2012, was effectively replaced by Popov.

Banners read "Popov as mayor means Kiev dies" and "Do not let Yanukovich steal elections from the people of Kiev" in the biggest such action this year by the united opposition which performed well in a parliamentary election in October.

But, despite impassioned pleas in the chamber by former economy minister Arseniy Yatsenyuk and far-right nationalist Oleh Tyahnybok, opposition parties failed to muster enough support to secure a June election.

Tuesday's demonstration came as Ukraine's leaders hesitate between forging closer ties with the European Union or aligning themselves more closely with former Soviet master Russia.

The European Union warned Yanukovich in February that a free trade deal could be jeopardised if Ukraine did not show progress towards political reform by May.

For the EU, the deal is conditional on improved human rights and ending the practice of "selective justice" - meaning the jailing of political opponents such as former prime minister Tymoshenko, Yanukovich's arch rival who is serving a seven-year jail sentence for abuse of office.

RE-ENERGISED OPPOSITION

Opposition parties, whose leaders also include world heavyweight boxing champion Vitaly Klitschko, have shown their teeth by paralysing parliamentary proceedings, often for weeks on end, by blockading the speaker's rostrum.

"This is not just about the Kiev mayoral election. If they put off this election, what do you think will happen to the presidential one? The same," Yatsenyuk said before parliament voted.

One of their central demands is the release from jail of Tymoshenko and her allies. Her continued imprisonment could now threaten free trade and political agreements with the EU which would anchor the former Soviet republic in the Western camp.

But Yanukovich, despite an often-stated commitment to taking Ukraine into mainstream Europe, has so far refused to bow to pressure either from the opposition or from Western governments and intervene in the case of Tymoshenko, his fiercest rival.

Although Ukraine is keen to cut its dependency on Russia, particularly its gas supplies, Kiev has yet to make a clear choice between a closer relationship with the EU or Moscow.

There has been strong speculation that one of Tymoshenko's jailed allies, former interior minister Yuri Lutsenko who is serving a four-year sentence for embezzlement and abuse of office, might receive more lenient treatment.

A Kiev court began hearing Lutsenko's appeal against his conviction and later adjourned until Wednesday.